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[tidla]

Is there a magic way to get steel bolts out of aluminium castings?

More and more cars are fitting aluminium suspension parts, the white powder corrosion seems to lock the bolts in mega tight.

Any suggestions?

[Andy H]

You need to keep moisture out of the screw thread so it needs to be assembled with grease/wax/Loctite* etc

*use one that doesn't set hard

[Bigron]

Good advice for before the steel bolt gets corroded in. However, once the horse has bolted......
Would it work if you warmed the aluminium casting, at the same time freezing the steel bolt with the freezing spray that plumbers use? The differential expansion rates of the two materiels, combined with steady, gentle pressure with a spanner on the hexagon might do the trick.

Ron.

[Andy H]

My experiences with ally castings on motorbikes as a teenager taught me that once the ally and steel had reacted and welded together the damage has been done.

[Bigron]

Tidla, what is your specific pronlem? With more detail, you might get more help.
Is the steel part too large to be dealt with by spark erosion?

Ron.

[cam.in.head]

It depends how bad it is corroded in. At work we deal with many aluminium casings and endplates on industrial fans and motors and lots of times we have to apply heat to release them. Most times  heating the actual bolt works,sometimes flicking the heat around the bolt shaft to heat the aliminium to almost melting point does it. Then the bolt should release.
With sheared off heads that you cannot put a saw slot into we usually have success by welding a nut over the remains and then trying immediately or further heating if required.
Sometimes plenty of release oil wd40 etc and carefull movement backwards snd forwards can work straight from cold if you are lucky.
Then for extreme cases we have to drill out ,starting small and central and increasing to size.

[tidla]

"Simple" job of replacing the discs and pads on an Audi A4 08 plate. Caliper carrier is made of aluminium. Spray and a 2 ton bottle jack did the job this time but the bolt was of reasonable size (21mm head ).

Smaller sized bolts are near impossible.

Heat is an option, just knowing how much to apply and would it really make a difference.

All the other suspension joints will need replacing at some point...

[Viral_Jim]

In terms of stopping it re-occurring when you refit bolts, I think Hylomar blue was originally invented for this purpose (by Rolls Royce aero I think). 

[78bex]

I once had to deal with a knackered 400 superdream twin I was using as a winter hack  & the spark plug on the right hand cylinder wasn`t gas tight in the stripped cylinder head.
I wasn`t gonna keep the bike so I used red locktite on the plug threads
After I ran the bike up to temp & let it cool off, that plug was never ever coming out again 

[78bex]

Now I think about it, that bike had over 60k miles on the clock & was  reliable
No oil leaks to speak off & reasonably quick for the day. I dropped her on an icey morning  & nothing fell off    the crash bars worked nicely

[TheBoy]

Now I think about it, that bike had over 60k miles on the clock & was  reliable
No oil leaks to speak off & reasonably quick for the day. I dropped her on an icey morning  & nothing fell off    the crash bars worked nicely

But IIRC, they weighed more than the moon

[78bex]

Now I think about it, that bike had over 60k miles on the clock & was  reliable
No oil leaks to speak off & reasonably quick for the day. I dropped her on an icey morning  & nothing fell off    the crash bars worked nicely

But IIRC, they weighed more than the moon

The centre stand became rusted in place, cos I managed to use it one night & the right hand leg of the stand sunk into the tarmac on Mum`s driveway 
 

[Bigron]

More or less on topic, but when I eventually get around to rebuilding my Sunbeam S8, I am fearful about just such a problem.
The engine and cylinder head are both aluminium, and I was wondering if it would be wise to Helicoil the spark plug threads and any other vulnerable tappings? Is there anything better than Helicoils?

Ron.

[Mr Gav]

Now I think about it, that bike had over 60k miles on the clock & was  reliable
No oil leaks to speak off & reasonably quick for the day. I dropped her on an icey morning  & nothing fell off    the crash bars worked nicely

But IIRC, they weighed more than the moon

They did but at least the 400cc gave it a bit more go unlike the 250cc I had